This invention concerns the generation and utilization of ultrasonic energy as it applies to ultrasonic tools; specifically to an ultrasonic tool providing a tip connected to a movable magnetic rod vibrated by closely positioned electromagnetic coils in a handpiece.
In the past, ultrasonic energy for applications, for example, dental scaling, was generated by use of magnetostrictive, piezoelectric, ferritestrictive, or air driven elements. Each of these methods has one or more disadvantages: heat buildup, power-control, high voltage requirement, fragility, limited or fixed frequency, limited or fixed type of motion generated, or production expense. These disadvantages can limit the devices from performing their intended purposes.
In contrast, an electromagnet is a well known device in which magnetism is produced by electrical current. When current is passed through a wound coil of several turns, the coil is magnetized, and resultantly when no current is flowing through the coil, the coil is de-magnetized. A metallic member, for example, iron, can be disposed along the longitudinal axis of a coil to increase the electromagnetic force generated. The strength of the magnetic field produced by an electromagnet is affected by such factors as the number of coils used, the number of turns in each coil, the magnitude of the current, and the magnetic permeability of the metallic coil material. The presence of an optional metallic member, for example, an iron core, can also affect the strength of the electromagnetic field.
The general application of stepper motors is well known. The use and theory of controlling current flow to the coils of a stepper motor through the use of a stepper motor control apparatus, sometimes also referred to as a driver or translator, is well developed. A stepper motor converts pulses of electrical current into specific rotational movements. A stepper motor can allow a “one phase on” stepping sequence or a “two phase on” stepping sequence, for example. A stepper motor can be “half stepped” by inserting an off state between transitioning phases and can utilize bipolar and/or unipolar winding, as is known in the art. A representative example of a stepper motor control apparatus is disclosed in U.S. Pat. No. 6,307,345, incorporated by reference herein.